To enhance metal biosorption capacity, magnesium chloride-modified Lentinula edodes (MMLE) was prepared by treating L. edodes with a mixture of NaOH, ethanol and MgCl₂. In this study, MMLE was successfully applied to remove Cd(II) and Cu(II) from aqueous solution with high biosorption capacities of 51.64 ± 0.65 and 59.03 ± 0.64 mg g⁻¹, respectively, which were higher than many other biosorbents. After pretreatment, the surface of spent L. edodes changed significantly and exposed more metal binding sites. When the initial concentration of heavy metal was 50 mg L⁻¹ and the biosorbent dosage was 5 g L⁻¹, the maximum uptake of Cu(II) and Cd(II) by MMLE at pH 5.0 and 25 °C was more than one order of magnitude higher than that of raw biomass. The equilibrium biosorption data of Cd(II) and Cu(II) could be well described by the Langmuir isotherm model. The experimental data obtained from the biosorption process was successfully correlated with a pseudo-second-order kinetics model. The thermodynamic parameters determined indicated that the biosorption process was endothermic and spontaneous. Both physisorption and chemisorption were involved in the biosorption of Cd(II) and Cu(II) onto the surface of MMLE through electrostatic interaction, ion exchange and complex formation. After three biosorption–desorption cycles, the biosorption and recovery efficiency of heavy metals from real industrial wastewater reached about 90% and 80%, respectively. The results show that MMLE could be an effective alternative biosorbent for the removal of heavy metals from real industrial wastewater.